The Amazons or Amazon Pirates are Nancy and Peggy Blackett. They are the owners of the Amazon dinghy. Though a very small crew, Nancy and Peggy are both very talented sailors, and have evidently made good use of their boat.
They function as a typical crew: Nancy gives orders, Peggy follows them. Peggy, the mate of the "Amazon" seemed to be in charge of the ship's food, like Susan, the mate of "Swallow" (SA11).
Although Nancy often refers to her younger sister as a "galoot" or "chump-headed galoot", they are clearly quite close, and Nancy relies on Peggy as a crew member just as Peggy relies on Nancy as a captain. Though Nancy is the more outgoing (and louder) of the two, Peggy is the more talkative, a habit for which Nancy frequently reprimands her.